1. Field of the Disclosure
The subject disclosure relates to assemblies and methods for sanitizing fluid such as water using UV light and, more particularly to extended UV sanitizing chamber ports that improve dosage as well as systems and methods for characterizing the sanitizing assemblies to improve operational efficiency.
2. Background of the Related Art
Generally, treatment of fluids via irradiation with ultraviolet light is known. The treatment of fluids, including disinfection of water, within an enclosed treatment zone that is irradiated with ultraviolet light (hereafter abbreviated to “UV” or UV light”) is shown in FIG. 6, which is a cross-sectional view of a system as described below. The objective of these systems, as for any type of photo-reactor, is to provide a uniform amount of UV energy to each individual element (e.g., contaminant molecule, microorganism) as the fluid passes through the treatment zone.
Typically the UV energy accumulated by an individual element while passing through the treatment zone is a product of the UV intensity multiplied by time of exposure and can be referred to as “UV dose” for that particular element. In practice, the elements flowing through the UV treatment zone will follow different paths, with these paths having different exposure times and flowing through areas of the treatment zone having different UV intensity. Thus, the end result is that the individual elements will accumulate different amounts of UV dose. In the case of UV disinfection reactors, the net efficacy is limited by the elements accumulating relatively low UV dose.
Still referring to FIG. 6, a typical prior-art UV treatment vessel 300 is shown in cross-section. In the vessel 300, a UV treatment zone 302 is defined within an interior chamber 304 of a housing 306. The housing 306 is fluid-tight except for an inlet port 308 and an outlet port 310. Fluid flowing through the chamber 304 is represented by flow arrows 312. At least one UV light emitting source 314 is located within chamber 304 to provide radiant UV energy within the treatment zone 302.
Many forms of UV emitting source assemblies 314 are available, including those utilizing mercury vapour lamps or UV light emitting diodes. The UV source 314 may be housed within a UV transparent sleeve 316. The UV source 314 receives electrical energy via wires 318 from an electrical power supply along with a microcontroller (not shown). The power supply and microcontroller are designed to suit the specific type of UV emitter 314.
A sealing cap 320 with an o-ring seal 322 seals the transparent sleeve 316 to the housing 306, allowing a passageway for the UV source 314 and wires 318 while preventing undesirable escape of fluid. The sleeve 316 may be physically stabilized by one or more mechanical supports (not shown) located along a length thereof. The supports are most commonly at the distal end 324 most distant from sealing cap 320.
The flowpath or fluid streamline as demonstrated by the arrows 312 has been analyzed using computational fluid dynamics and numerical methods for modeling dose accumulation for individual fluid elements. As a result, it is known that certain fluid elements take a more rapid transfer through the treatment zone 312. For example, fluid elements following the streamlined flowpath of arrows 312 will have a relatively shorter duration of exposure time. Additionally, these fluid elements experience a relatively low radiant intensity due to farther distance from UV source 314. In short, certain fluid elements such as the ones along arrows 312 are poorly dosed. It is also appreciated that the fluid will have a higher velocity in the region 338 near the outlet port 310.
Further, the UV source is often a low pressure (LP) or low-pressure high output (LPHO) mercury vapour lamp that relies on liquid mercury droplets within the lamp envelope to regulate mercury vapour pressure during lamp operation. The UV light output efficiency of such lamps is strongly dependent on the pressure of the mercury vapour inside the lamp.
Devices utilizing UV outputs of mercury vapour lamps are well known. More particularly, mercury vapour lamps emitting ultraviolet light in the UVC wavelength regions near 254 nm and 185 nm are well known in fluid treatment applications. The characteristic wavelength outputs are commonly used to provide germicidal, oxidizing, and other beneficial effects. Often there are single-lamp point-of-use water treatment systems as well as multi-lamp systems for larger flow-rates.
It is apparent that the overall efficacy of the fluid treatment system benefits from having efficient production of UVC light from electrical energy input to the UV lamp. Although the family of LP and LPHO lamps represents one of the most economical means of producing germicidal light, it suffers from loss of output efficiency if the liquid micro-droplets are either below or above the temperature required for optimum germicidal light output. Since these UV systems must typically treat fluids across a range of temperatures, the lamp ballast/controller must be able to provide sufficient energy to ensure UVC output for fluid at the low end of the temperature range.
Unfortunately, with conventional ballasts supplying constant are current, the high energy required for cold operation results in the lamp(s) operating in an overheated condition when fluid is at higher temperatures, and in cases where the fluid is stagnant the UV lamp causes undesirable additional heating of the fluid. In practice, it is problematic to match a particular lamp and driving current to satisfy fluid treatment applications across a range of fluid temperatures. Thus, the lamp UVC efficiency can be reduced to less than half of the peak just from overcooling or overheating of the lamp.